Slavica Radjen1,2, Stankovic-PopovicV3
1Institute of Hygiene, Military Medical Academy, Belgrade, Serbia
2Medical Faculty of Military Medical Academy University of Defence in Belgrade, Serbia
3Clinical department of Nephrology and Metabolic Disease with the Center for Dialysis, Zvezdara University Medical Center, Belgrade, Serbia
Protein-energy malnutrition (PEM) is common complication in peritoneal dialysis (PD) patients and contributes to morbidity and mortality. PEM results from a decreased energy or protein intake as compared to actual needs. There are several factors that can contribute to the development of malnutrition that are relatively specific to peritoneal dialysis: losses of protein and amino acids into the peritoneal dialysate; dialysate in the abdomen impart a feeling of fullness that decrease the appetite; hyperglycemia, which can be induced by the absorption of glucose from the dialysate, may suppress appetite.
There is not a single measurement which can be used to determine the presence of PEM.
Therefore, malnutrition should be diagnosed by a number of assessment tools including dietary assessment, anthropometry, subjective global assessment and some biochemical examinations that correlate with nutritional status.
In order to prevent malnutrition, periodic assessment of nutritional status should be part of the routine care of dialysis patients to permit early recognition and the institution of appropriate therapy. The nutritional status of the patient should be reassessed every 3–6 months and the dietary regimen should be modified according to changes in patient preferences and clinical status. Early identification of malnutrition and optimal use of diet, the dialysis dose, and perhaps supplements will lead to an improvement in nutritional status and patient outcome.
Key words: malnutrition, chronic kidney disease, peritoneal dialysis.
Protein-energy malnutrition is common complication in PD patients which contributes to morbidity and mortality and affects their survival and quality of life. In PD patients the prevalence of PEM varies, according to the considered nutritional parameters, from 18% to 56%
PEM results from a decreased food intake as compared to actual needs. Multiple factors can affect nutritional status of dialysis patients: restrictive regimens, inadequate dialysis, frequent hospitalization, multiple medications, comorbidities, uncontrolled anaemia, uremic toxins, gastroparesis, exocrine pancreatic insufficiency and reduced mucosal enzyme activities, altered plasma amino acids and neurotransmitters synthesis, inflammatory cytokines, depression, low social status, solitude and an inability to prepare meals.
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There are several factors that can contribute to the development of malnutrition that are relatively specific to PD such as losses of protein and amino acids into the peritoneal dialysate, dialysate in the abdomen impart a feeling of fullness that decrease the appetite, early satiety or feelings of fullness, suppression of appetite due to the abdominal distension, suppression of appetite induced by the absorption of glucose from the dialysate, impairment in gastric emptying due to the instillation of dialysate.
There is no single measurement which can be used to determine the presence of malnutrition Thus, malnutrition should be diagnosed by a number of assessment tools including history and physical examination, dietary assessment, anthropometry, subjective global assessment and some biochemical examinations that correlate with nutritional status.
History and physical examination
The history and physical examination can often provide important data which can direct to the patient who might be malnourished. These include symptoms such as nausea, vomiting, anorexia, weight loss or gain, and presence of concomitant problems that can affect nutrition, such as alcoholism, diabetes mellitus, and gastrointestinal disease. Besides, it is necessary to pay attention to some psychosocial issues such as access and affordability of food, and ability to prepare meals. Signs or symptoms of depression should also be identified, since clinical and nondialysis days). It is very useful, especially if the patient weighs the portions of food.
Anthropometry
Anthropometric measurements provide a rapid, easily performed noninvasive method for evaluating body composition. It is best if serial measurements are carried out by the same observer. If this isn't feasible, it somewhat limits its usefulness. PD patients often have PEM with a reduction of both fat mass and lean body mass. Therefore, assessment of body weight, subcutaneous fat mass and muscle mass are important part of routine nutritional assessment.
Body weight is the simplest and most effective indicator of energy intake and it should be measured regularly. Unplanned weight loss should always be investigated. An unplanned weight loss greater than 10% occurring over 3 months or less has a negative prognostic value.
Of course, in a PD patient, edema may be responsible for an increase in body weight. Body mass index (BMI) is also important and easy to determine, although BMI is more useful for the assessment of obesity than of malnutrition.
Body fat is estimated by measuring skin fold thickness at four sites, while mid-arm circumference and mid-arm muscle circumference can provide an estimate of the muscle mass.
Hand-grip strength is a cheap and simple method that agrees reasonably well with other measures of nutritional status and predict outcome in PD patients. Thus it may be recommended for routine follow-up of PD patients.
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While anthropometry has the advantage of being simple and quick to carry out, there are less precise than DEXA. There is good correlation between those techniques and that each could be readily used in stable dialysis patients. DEXA is fairly expensive and not always readily available. DEXA should be reserved for selected patients. BIA is not recommended for routine assessment of nutritional status. Thus, at present, anthropometry is the only method that can be readily performed in most units.
Biochemical parameters
Measurement of several circulating proteins has been used to assess nutritional status in PD patients. There are, however, potential limitations to their use in this setting due to changes in protein distribution or metabolism by renal failure or comorbid conditions. Because of that, interpretation of the values obtained should be undertaken with caution.
The plasma albumin concentration correlates well with body protein stores. Since albumin has a long half-life and hepatic synthetic reserve is very large, hypoalbuminemia is a relatively late manifestation of malnutrition. Several studies have demonstrated a negative correlation between the plasma albumin concentration and mortality in PD. The increase in mortality with hypoalbuminemia appears to occur even at near normal albumin levels. CANUSA study has shown that each 10 g/L increase in the plasma albumin concentration decreased the relative risk of death by 6% in PD patients.
However, serum albumin also reflects several non-nutritional factors which are frequently present in PD patients, including infection, inflammation, hydration status, peritoneal and urinary albumin losses, and acidaemia. Thus hypoalbuminaemia in PD patient may not always result from PEM and albumin alone is not a clinically useful measure for PEM. The serum albumin concentration should be measured monthly.
Prealbumin has a shorter half-life than albumin, has a close relationship with nutritional status and is a good predictor of clinical outcome, but it is a negative acute phase protein as well as albumin.
Low transferrin levels have been described in dialysis patients and have been ascribed to malnutrition. However, plasma transferrin values are frequently reduced in renal failure independent of malnutrition, perhaps due to fluctuations in iron stores.
Protein Equivalent of Total Nitrogen Appearance (PNA) is a valid and useful measure of net protein degradation and protein intake in PD patients. There are some limitations to its use. In the clinical stable patients it can be used to estimate protein intake. In the catabolic patient PNA will exceed, while, in anabolic patients PNA will underestimate actual protein intake.
When the protein intake is less than 1 g/kg/d PNA may overestimate dietary protein intake. In obese, malnourished, and edematous patients, normalizing PNA to body weight can be misleading.
The serum total cholesterol concentration is reduced in malnourished patients. It is less sensitive nutritional marker, but is cheap and easily available.
Subjective global assessment
Subjective global assessment (SGA) is a useful valid clinical instrument for assessing the nutritional status of PD patients. It is inexpensive and it can be performed rapidly. It gives a global score of protein-energy nutritional status. The SGA is based on history and physical examination. It focuses on gastrointestinal symptoms (anorexia, nausea, vomiting, diarrhoea),
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weight loss in the preceding 6 months, and visual assessment of subcutaneous tissue and muscle mass. Scores are subjectively rated on a four-point or seven point scale. The use of the seven point scale is recommended because of its greater sensitivity and its use in large epidemiological studies such as the CANUSA study. SGA has a high predictive value for mortality, but one potential problem with SGA is its subjective natures, which may reduce its reproducibility. The European Best Practices Guidelines also suggest that monitoring include a subjective global assessment.
Monitoring
Nutritional status of the patient should be assessed at the start of PD and reassessed every 3–6 months. Unstable and malnourished patients may require monitoring at shorter intervals.
Some parameters such as albumin should be evaluated monthly.
Conclusion:
Malnutrition is higly prevalent among PD patients. In order to prevent malnutrition, periodic assessment of nutritional status should be part of the routine care of dialysis patients to permit early recognition and the institution of appropriate therapy. The routine assessment of nutritional status involves evaluation of dietary intake, anthropometry, laboratory and clinical examinations. The nutritional status of the patient should be reassessed every 3–6 months and the dietary regimen should be modified according to changes in patient preferences and clinical status. Early identification of malnutrition and optimal use of diet, the dialysis dose, and perhaps supplements will lead to an improvement in nutritional status and patient outcome.
References:
Canada-USA (CANUSA) Peritoneal Dialysis Study Group. Adequacy of dialysis and nutrition in continuous peritoneal dialysis: association with clinical outcomes. J Am Soc Nephrol 1996; 7: 198–207.
Carrero JJ, Aguilera A, Stenvinkel P et al. Appetite disorders in uremia. J Ren Nutr 2008; 18:
107–13.
European best practice guidelines for peritoneal dialysis. 8 Nutrition in peritoneal dialysis.
Nephrol Dial Transplant 2005; 20 [Suppl 9]:28-33.
Han SH, Han DS. Nutrition in patients on peritoneal dialysis. Nat Rev Nephrol 2012; 8: 163–
75.
Heng AE, Cano NJM. Nutritional problems in adult patients with stage 5 chronic kidney disease on dialyse (both haemodialysis and peritoneal dialysis). Nephrol Dial Transplant Plus 2010; 3:109-17.
K/DOQI, National Kidney Foundation. Clinical practice guidelines for nutrition in chronic renal failure. Am J Kidney Dis. 2000;35:S1-140.
Locatelli F, Fouque D, Heimburger O, Drueke TB, Cannata-Andia JB, Horl WH at al.
nutritional status in dialysis patients: a European consensus. Nephrol Dial Transplant 2002;
17: 563-72.
110
Nazanin N, Kovesdy CP, Murali S, Benner D, Bross R, Block G at al. Dietary assessment of individuals with chronic kidney disease. Semin Dial 2010; 23(4): 359-64
Pasticci F, Fantuzzi AL, Pegoraro M, McCann M, Bedogni G. Nutritional management of stage 5 chronic kidney disease. J Ren Care. 2012; 38(1): 50-8.
Wang AY, Sanderson J, Sea MM et al. Important factors other than dialysis adequacy associated with inadequate dietary protein and energy intakes in patients receiving maintenance peritoneal dialysis. Am J Clin Nutr 2003; 77: 834–841.
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